1. Field of the Invention
This invention relates to a slide fastener shortening method and its apparatus for shortening a length of a slider fastener, particularly a slide fastener having rows of fastener elements made of synthetic resin from a predetermined length of the slide fastener into a desired short length thereof.
2.Prior Art
Conventional slide fastener shortening process for shortening the length of the slide fastener in accordance with the stitched garment of the slide fastener, have heretofore been proposed. These conventional processes used various methods and apparatus for removing unnecessary fastener elements from the slide fastener of a predetermined length to form a space section, and involved cutting the slide fastener at the space section into the desired length to provide the product slide fastener of a desired short length. One method for removing the unnecessary fastener elements to form the space section is shown in J P, B no. 48-3222 (Japanese Patent Publication), wherein a method includes the steps of: compressing and deforming leg portions of fastener elements to be thin in order to permit easy deformation; pulling the neighboring fastener tape right and left in a direction orthogonal to the fastener tape; and forcibly drawing and removing the fastener tape from the leg portions of the fastener elements to form the space sections free of fastener elements. Another method is shown in J. P. B. no. 57-61407 (Japanese Patent Publication), and includes the steps of:
holding the fastener tape with beaded portion between a pair of dies provided with protruded blades which are inserted from the back into between the fastener tapes and the leg portions to spread them apart;
pressing interengaging head portions of the fastener elements by moving a punch downwardly;
and striking the protruded blades of the dies into the space between the leg portions of the fastener elements and the fastener tapes to spread the head portions of the fastener elements apart, so as to form space sections free of the fastener elements.
However, the former space section forming method suffers from several drawbacks. For example, when the fastener tapes are pulled left and right in the orthogonal direction to draw the fastener elements forcibly, thinned fastener elements get broken, often leaving a part of the broken fastener elements still adhered to the fastener tapes. And, since each fastener tape is drawn and removed in a direction orthogonal to the longitudinal direction of each fastener chain, the fastener tape is moved in the orthogonal direction and it becomes difficult to continue operating the subsequent cutting process.
The latter space section forming method suffers from the drawback that, since the protruded blades provided with the dies are set to contact the fastener tape surfaces, when the interengaging head portions of the fastener elements are pressed by the punch to strike the protruded blades in the fastener tapes, the fastener tapes are frequently damaged.